Tools You Will Need for this Job

You may need to acquire a couple new tools to implement repairs on your
keyboard. This list is generic, but there are a couple of specific part
numbers in the
following text,
should you wish to look for something in a catalogue.

0.05" (1/20th of an inch) or 1.27mm (millimetre) hex driver (T-5 torx
driver will also work in a pinch)

2mm or 3mm slot (flat) screwdrivers, two of them, which can be found in
jeweller’s sets

electrically conductive paint (like automotive rear window defogger paint)
or some other highly-conductive material that can be easily applied

Phillips screwdrivers in sizes 2, 1 and possibly zero

an ohmmeter or digital multimeter for measuring resistances of traces
during troubleshooting

What Not to Do with your Expensive Keyboard

The contents of this page is very simple in nature but explicit in execution.
When the keyboard you rely on for your daily work costs more than one hundred
dollars and you have no spare, you should not attempt to test its limits by
forcing it to eat the crumbs from the bottom of your bag of Doritos, and
especially do not try to force feed your keyboard a can of soda!

The latter of the examples above is definately the most catastrophic, and it
is the very reason this page now exists. Because the Apple Pro Keyboard is not
your average $15 replacement you’ll find everywhere for your IBM compatible,
it is viable to disassemble and repair it in house, provided you’ve got the
patience, tools and skills.

Here in painstaking detail, the method of ripping apart an Apple Pro Keyboard
and giving it a thorough cleaning is presented. Found a key that refuses to work
at all? As was the case with the keyboard that inspired this article, one or more
keys may not function if the keyboard gulps down a soda. Presented here also is
the fix for that.

Note that the keyboard represented here is model M7803 and your mileage may
vary as to whether or not this article is useful for your particular keyboard.

Note that if you are just reading this article for the purpose of giving your
Mac keyboard a thorough cleaning, there are some important points in the
cleaning
section you should keep in mind.

First Aid for your Keyboard

Have you gone and done it recently? For your sake, hopefully within the last
five minutes or so? What you should do immediately after your keyboard soaks up
any of your delicious beverage choices is unplug it from the computer, and then
drain it. Drain slowly at first, and always in one direction.

Tilt the keyboard slightly so that a front corner (left or right) is pointed
down and is the only area draining liquid. As the flow slows, gradually lift the
keyboard higher, ensuring that just one corner is pointed down instead of one
entire end of the keyboard. This action helps ensure that potential damage is
confined to one area of the keyboard — hopefully, anyway. The gentle
tilting at first helps to keep the liquid from soaking through all the layers of
the innards from top to bottom. Ideally, if you’ve followed this procedure
quickly enough, you’ll be left with a keyboard that still works when you
turn it on again. But DO NOT test that theory yet!

Prevention is Better than Problems

Most restaurants that you visit will have a computer system of some form or
another and it is most likely that each computer also has a keyboard attached.
If you look closely you will likely see that every keyboard is protected in one
way or another. Why?

Granted, keyboards can be extremely cheap these days. Some are so inexpensive
that the protective cover for the keyboard costs the same, or more than the
keyboard itself. The real reason for this seemingly silly idea is actually money.
A dysfunctional keyboard in a restaurant only costs $10 to replace when the
restaurant is closed. When it is open for business, that same broken keyboard may
cost thousands of dollars in lost revenues!

You can ask any restaurant manager what happens during the rushed dinner hours
when a computer fails to work, or worse, when they all fail. Granted, not every
keyboard has such a high status in the world, but good user habits will certainly
not go unrewarded. Keep your food stuffs away from your computer and especially
its vulnerable keyboard. After all, even a $10 keyboard is better than nothing
when your essay, thesis, film project or board room presentation is due by 9:00am
and that’s only nine hours away. Just where do you buy a keyboard at
midnight, anyway?

And, having stated all that I would also like to point out that the time
taken to go ahead and clean your keyboard is not your average 15 minute quick fix.
Don’t you have people to see, places to go and better things to do with
your time in general?

Disassembly of the Apple Pro Keyboard

The Apple web site seems to be completely lacking in its ability to help you
out in times of dire need when it comes to keyboard cleaning and repair, so here
is how you might figure it out.

First, flip the keyboard over on its face and stare blankly at those four
allen screws found near the top left and right edges. The hex key you will need
for this job is 0.05 inches in diameter (one twentieth of an inch). If by chance
you have Xcelite hex drivers in your tool caddy, the part number 99-20, or LN-20
may be marked on it. The metric size is 1.27 millimetres, which happens to be
exactly one twentieth of an inch, so if you have only metric tools, use a 1.27mm
allen driver (Xcelite part number LN-1.27mm) to remove these four screws. In a
pinch, you could even use a Torx size 5 (T-5) driver without danger of stripping
the heads of those hex screws. Thanks to Joe Wheeler for pointing that out, as
his experience of trying to find an appropriate hex driver was arduous and
fruitless.

Another option for tools is this nice looking set of Lux Tools from Germany. Part
number 585 395 (EAN CODE 4007875853959) is a complete set of screwdriver bits with
the sizes and types needed for working on the Apple Pro Keyboards. My thanks go
to Gregor Komauer for the photo and the tip about this set.

Now, before you read any further and do anything (de)constructive, HEED THIS
WARNING: The screws used to hold the keyboard together the cheapest of the cheap!
In other words, use your newest, sharpest, and best tools for this job, and apply
firm pressure to hold the allen key or screwdriver bit in place while you remove
any screws! This will prevent you from stripping the heads from the screws and
rendering them useless. Care to look in stores for replacements? I’d bet
they are not easy to find—but I have been wrong before and if you know of
a place, please find the e-mail link at the bottom of this page and let me know
what you have found so I can post it for others to see.

Likewise for any reassembly, use good tools but at this time DO NOT use much
force to replace the screws. They will strip easily, and while a couple missing
screws may not mean you have to junk your keyboard I don’t for a moment
suggest you try your luck—after all when you go through this process it is
not quick and painless, so ensure that you use care and make the endeavour
worthwhile.

Notice that when these four screws are removed there are two pairs, each having a
different length. This is important for proper reassembly later, so remember that
the shorter ones are for the outer edges and the longer ones are used closer
toward the keyboard’s centre. You can see in the image at right a few spots
of cola that ended up at the bottom of the keyboard. Notice that near the bottom
of the keyboard on the left and right ends there appear to be two more screws that
grip the underside of the keyboard. If the keyboard is tilted sufficiently you
can also find a third screw secluded by the lovely Apple logo in the centre of the
shell. These screws are accessed from the top by removing the appropriate key caps
thusly:

Gently pry the key caps out of their resting places using a small slot-tipped
screwdriver. Get the screwdriver tip under the key cap first, then lower the
handle onto the adjacent key cap so the screwdriver becomes a miniature prying
lever. The key caps will snap out of their holders easily, but be gentle and
patient so the snaps do not break off during the process. To get at the three
hidden screws you will need to remove these key caps: the CAPS LOCK, the SEMICOLON
and the 6 (six) key of the numeric keypad.

At this point you might as well remove all of the key caps as they must come
off later in the process anyway. This will also make it easier to separate the top
and bottom shells from each other when that time comes.

A look under the CAPS LOCK key reveals a few more cola blotches and the hole where
one of the three hidden screws normally resides to keep the keyboard together. This
image also shows the LED which glows green when the caps lock function is in use.
Because the key caps are translucent, an LED shows through them. Note now that
losing one of these LEDs is easy to do if you are not meticulously careful while
disassembling this keyboard—they just sit there, sandwiched between the top
shell and the membrane. You can buy green LEDs of the appropriate size to replace
a lost one at any good electronics supply shop. But the process of cutting and
bending the leads to just the right angle so that they don’t puncture the
membrane is tricky, and perhaps not worth it in the end.

There is one last hidden screw to remove before the keyboard shells will come
apart and it lies beneath the Apple Pro Keyboard label on the underside shell.
Locate it by applying pressure to the label with your index finger located just
left of the small Apple logo on the label, and just above the first digit of the
serial number label. The label will give slightly where it covers the screw hole,
and once you locate it properly you can simply drive a small screwdriver through
the label and use a No. 1 or No. 2 Philips screwdriver to remove the screw. If you
don’t want to put a hole in your label, read on.

IMPORTANT: The plasticized sticker must be pierced or removed in order for the
screw to become accessible. Once you have properly located the indentation in the
sticker using the above (or similar) method, punch through the sticker with your
screwdriver to get at that screw.

An option to putting a hole in your keyboard sticker is to carefully peel it
away from the back side of the keyboard. You can use a dull knife or some other
thin, flexible or curved blade to gently lift the corner of the sticker. Being
careful not to touch the adhesive of the sticker with your fingers (or any other
contaminant,) pull the sticker away from the keyboard at a 45 degree angle. This
is important, as if you pull the sticker away at a sharper angle it will likely
develop a permanent curl. With such a sticker it will be difficult to reapply it
and have it look as good as before. Leave the screw out once you remove it so
you’ll never have to peel away the sticker again in the future.

NOTE: If you try the sticker peel-away method and find that later the corner
won’t stay stuck when you reapply it, just use a small piece of transparent
tape or a tiny drop of plastic cement. Now the tedious task of separating the
shells begins!

The photo at right shows the top keyboard shell and the photo at left is a
close-up showing the snap together nature of the top and bottom shells. The oval
hole in the top shell mates with a similar oval nib molded into the bottom shell.
There are nine of these atrocities along the front edge of the keyboard and
separating the two shells from each other is a slow, gentle, tedious
trial-and-error process with miniature slot-tipped screwdrivers or similar tools.
Bob Palmer wrote to suggest that prying the four contact points at the back edge
of the keyboard away from one another with a nail file was easier. Alternately
and perhaps safer, you can use your fingers if you have all the key caps removed.
Place your fingers where the space bar usually resides, and your thumbs against
the front-most edge of the bottom shell. Holding on with the keyboard in a position
where you might normally be using it, apply pressure towards your belly to release
the front edge of the top shell from the bottom shell. You should be able to
separate the two pieces without breaking any supports or snaps. My thanks to Paul
Ossenbruggen for this suggestion.

In order to fully separate the inner keyboard assembly from the bottom shell you
must remove the keyboard cable strain relief. Once these two screws have been
removed just pull the cable straight up off the bottom shell about an inch to
release the strain relief mold from the bottom shell.

The printed circuit board (PCB) is next on the list of items to remove. A grey
coloured protective plate normally hides the PCB from plain sight, but it falls
away from the PCB as the inner keyboard assembly is removed from the bottom shell.
This cover also helps to hold the USB ports in place when the keyboard is fully
assembled.

Note that pan head (or round head) Philips type screws are used to hold the PCB in
place while the other screws found in the back plate have bevelled heads so they
rest just below the surface of the back plate when installed properly. Remove all
the pan head screws from the PCB.

The last screw to remove to get the PCB assembly away from the back plate is the
grounding screw. Note in this image that there is also a lock washer between the
ground wire lug and the screw hole in the back plate. Keep the lock washer handy
with the ground screw for later reassembly.

At this point note that removal of all the key caps is recommended, if you
haven’t yet done so. Use care and have patience while removing all of the
keycaps so they don’t go flying and get lost or broken.

After removal of the PCB board, USB connectors and key caps, the decorative back
plate cover must be lifted off to reveal over thirty small screws with bevelled
heads underneath. The cover is simply a silvered piece of card stock (paper) that
is held on by an adhesive. It will tear under the excessive stress of a sharp
object, so exercise care in removing it. Mike Skaggs suggests using a metal
bookmark, or a sufficiently stiff plastic one to slide under the edges of the card
stock. Keep the bookmark flat against the keyboard, just as the card stock is.
Work your way around all the edges sliding the bookmark sideways, easily peeling
away the adhesive while preserving the integrity of the card stock. The screws
beneath the card stock hold the key button position molding in place over the
keyboard membranes. They also ensure that the keyboard membranes rest flat
against the back plate which translates into a higher degree of reliability and
extended keyboard life. Remove all thirty-nine (39) of these bevelled head screws
to get at the real meat and potatoes of the disassembly operation.

Principal Components of a Membrane Keyboard

This is the top view of the keyboard inner assembly showing the key button mold
which holds in place each of the key buttons and key caps. After the bevelled head
screws are removed from the back plate, this plastic piece will come away freely,
as will all the key buttons themselves. Due to static attraction, some will stick
to the top keyboard membrane and some will fall away with the key button mold.
Again, use care when separating the layers here so none of the pieces get lost.
Prone to hiding easily are the LEDs, the key buttons and the two pressure strips
(usually white or clear jelly-like strips) which reside near the top of the
keyboard.

This is one key button. It is an elastic type of material which springs back into
form after squishing. There are 108 of these, one per key on the keyboard. If you
lose one, you lose the function of one key. These devices have a built-in plunger
that—when pushed down by a key cap—pushes down on the top keyboard
membrane and forces it to connect with the lower keyboard membrane, thus creating
a connection which translates into a key press.

This photo depicts each of the three membrane layers that make up the electrical
matrix for the keyboard. The top and bottom layers have electrically conductive
paste screened onto them during manufacture. These pastes are cured into hardened
electrical conductors with a rough surface. The uneven, sandpaper-like surface
helps ensure a good contact by providing several electrical connection points with
every keystroke. The middle membrane layer is the separator, which has one small
hole punched into it for every key. The hole is not much larger than the plunger
that is built into the key button. This separator keeps the top membrane from
coming into contact with the bottom membrane until a deliberate key press is made
by the computer user. The tracks of green in this image are insulating coatings
which ensure that the traces running between all the key pads will not come into
electrical contact with each other through keystrokes or other external pressures.
Even water or alcohol will not get under these coatings, which is good to know
for cleaning purposes.

Damage and Controlling It

Seen here are the remains of last night’s drinking party for this keyboard.
The cola deposits are pretty easy to spot, but should your keyboard have swallowed
a clear soda beverage, be sure to locate all the sticky spots for a thorough
cleaning.

This keyboard still worked great, save a single key. The acid(s) in soda
beverages digest the trace materials and can destroy the electrical connection
between a keypad and its conductive trace which leads the key press signal to the
computer. In the digitally enhanced photo on the left, the blackened areas are the
points where the conductive material has been eaten away by the acid(s). On the
right is a comparison photo showing contacts that have not been attacked by soda
acids. The longer the keyboard sits uncleansed of soda beverages, the greater the
damage that will occur. Notice the complete lack of any silver conductive paste
between the original keypad printing and the green insulated trace portion. This
key no longer was functional after the acid damage. See the section on repairing a
digested keypad (below) for information on how this problem can be located and
resolved. Basically, the sooner you can clean a dripping wet keyboard, the better.

Cleaning a Keyboard

It is likely that nearly every single component of a keyboard should be
cleaned if there was a soda mishap. If your keyboard problems stem from too many
food crumbs inside, you can probably skip a couple of the steps outlined here.
First, locate the spot in the middle of this image. This is a rough patterned
circle to the right of centre where all three membrane layers have been fused
together. The number one rule here is DO NOT DISTURB! If you
tear the layers apart it will be difficult to perfectly align them in the future,
and proper reassembly of the keyboard will be a long, trying process. While
cleaning the membrane layers, try not to pry too hard against this fused spot and
all will be well.

You can cleanse the keyboard membranes using either water or alcohol. In
either case be certain that each layer is perfectly dry on both sides before you
sandwich them together again—especially if you use water. And if you use
alcohol, do not bathe it in the alcohol. If there is enough liquid sandwiched
between the layers they will stick together in a manner that makes it very
difficult to properly align them for the reassembly process. Use a damp,
lint-free cloth or a quality paper towel wetted with the water or alcohol and
gently rub it back and forth over the surfaces to be cleaned.

CAUTION: While cleaning the membranes, be careful not to fold or crease them
as the reliability of the keys in the vicinity of the fold may be hampered. It is
also possible to break the electrical connection if the crease is acute enough.

CAUTION 2: DO NOT USE HEAT to dry any part of the keyboard. No hair
dryer, no blow torch, no hanging out to dry in the sun—nein!!! Your keyboard
detests heat even more than it does liquid beverages. You may use cool air only,
and if you have an air compressor it will work just fine, but use care with that
too as pieces will fly into corners where you will never find them if you start
simply blasting them with high pressure streams of air.

CAUTION 3: NO SOLVENTS! In case you are tempted to use anything but water to
clean your keyboard, DON’T. You may not have any keyboard left to
speak of if you apply the wrong kind of solvents to the delicate plastic parts of
your keyboard. Use water only.

CAUTION 4: ISOPROPYL ALCOHOL—This is my preferred solvent for cleaning
just about anything, and I did use it to clean the keyboard in this article.
Having said that, I now recommend against it unless totally necessary. As Ian
Lanham wrote in to describe his now discoloured (i.e. not transparent) key button
mold which happened because he left his soaking in 91 percent isopropyl alcohol,
I now caution against using anything but water. The flipside of this is that you
can safely use isopropyl alcohol but for mechanical cleaning only. In effect, you
could use it when cleaning with a cotton swab, lint-free napkin, or similar
but never use it for soaking applications… use distilled water only if
you intend to soak your keyboard parts.

The photo at left shows the back plate of the keyboard. It will likely need a
rinse with water if there was any soda beverage found elsewhere in the
keyboard. On the right is a detail photo showing the key button mold. This piece
will certainly need a rinse if liquid contacted the keyboard. Using alcohol here
will allow the cleaning to be quicker because the alcohol will evaporate much more
quickly than water, but be sure not to let the piece rest in a bath of alcohol.
If you have a pressurized air source—such as a hose linked to an air
compressor—you can blow the bulk of the water away speeding up the process
a lot if you choose to use water only.

WARNING! Do not attempt to apply heat with a heat gun or hair dryer. Did I
mention this already? It’s important, so read it again! One wrong move and
you’ve warped the mold and probably made the keyboard useless. The stuff is
all plastic and the screws that hold it together bite into that plastic. I will
spell it out here—too much torque and the screws will tear the plastic apart,
defeating their original purpose of holding it together. Correcting a warped mold
via the backplate screws can prove to be a futile effort. While on the subject of
screws going into plastic, assure yourself that they are going in their original
spiral grooves by first rotating each screw counter-clockwise while gently pushing
it down into its hole in the plastic. Rotate until it clicks at which point you
know it has seated its threads into the originally cut threads of the plastic,
then tighten as normal. Using this method ensures you do not continually cut a new
path for the screw every time you remove then replace the screw, and therefore
retains the holding power of the plastic.

Here is a picture of all the small key caps in a bucket of water. The water
will dissolve any soda residue and leave the key caps nice and clean. Alcohol
will evaporate from a soaking wet key cap in far less time than water, but beware
that alcohol is a solvent and can damage or change the colour of plastic parts.

Here is the method of choice when it comes to removing water from plastic parts.
A high pressure, high volume air source will disperse the water quickly and dry
the pieces more quickly than you could expect to do so any other way. There is one
thing to keep in mind no matter what you bathe the key caps in, however; do not
bathe the larger keys such as the SPACE BAR or the ENTER, RETURN, SHIFT keys, etc.
All these larger keys have wire supports to even out the pressure exerted upon
them by the user, and direct that pressure to the key button belonging to the cap.
To go along with the wire support is grease at each point where the support comes
into contact with any plastic bits.

CAUTION: The grease needs to remain in place to prevent the wire supports from
scraping the plastic pieces they touch into plastic filings over time. This is the
reason you should not immerse any of the larger keys containing these wire
supports in any sort of bath, especially alcohol which will likely wash all the
grease away. You can add a good twenty minutes to the project if you need to put
fresh grease on all those contact points, so instead of bathing them, just use a
dampened cloth to remove any food stuffs that may be sticking to those larger key
caps.

NOTE: If you must clean the grease away from the larger keys, you must replace
the lubricant where the wire supports pivot under the key caps. Use petroleum jelly
(e.g. Vaseline) or some other relatively benign lubricant. Be careful here as many
lubricants have solvents and you may find yourself wishing you never tried to
regrease the key caps!

Repairing a Digested Keypad

On the left, again, the enhanced photograph showing the damage to the keypad
caused by the acid(s) found in many soda beverages. On the right, the unenhanced
portrait of the same keypad after some conductive paint from a circuit trace
repair pen was applied to the area between the insulated trace and the centre of
the keypad. NOTE: If you perform this repair and find in testing that the trace
did not become a complete circuit again, try carefully scraping off some of the
green insulating layer beside the damaged area first, then redraw the trace with
your conductive pen or paint. Sometimes the damage can reach beneath the
insulating layer. Note that you may also use rear window defogger repair paint
which can be found at almost any automotive parts store. Make sure you let that
paint dry completely before reassembling your keyboard for testing.

If your can or pen of conductive paint says something like “better
results may be obtained by using heat to cure the paint” I’m telling
you now that YOU DON’T CARE! That’s right, don’t mind the
directions at all because as you ought to know by now, your Apple Pro Keyboard
does not like heat! If the paint must cure, let it do so at room temperature only,
and just let it cure for perhaps four or five times the duration suggested in the
“apply heat” method. All will be well. Now continue on!

Locating the Problem

The keypads on a keyboard are arranged in a matrix, and so an entire row (or
more) of keys may have one common conductive path between each and every keypad in
that row. To locate the exact spot where the dysfunctional key has been damaged,
you can use an ohmmeter—which measures DC circuit resistance—and
pinpoint the problem area by the process of elimination. From one end of the
keyboard to the other along a single path, the resistance should be no greater
than about twenty (20) ohms. A marked increase from this guideline indicates a
poor connection and a potential problem.

Start by placing one of the leads of the ohmmeter on the centre of the keypad
under the key which fails to work. Determine by visual inspection the next closest
keypad in that same circuit and place the second lead of the ohmmeter there to
measure the resistance from the broken key to the next. If the resistance is
high—above a couple hundred ohms—then the conductive path between
those two keys is not ideal and may be the cause of the fault. In the case of this
keyboard, the resistance from one key to the next closest was more than 10k
(ten thousand) ohms. Chances are excellent that the problem is between the keypad
itself and the border to the conductive trace that runs between the bad key and
the next closest. This trace will be covered over with a green insulating plastic
layer.

Apply some conductive paint starting at the edge of the insulator next to the
bad keypad and draw a new path with the paint into or near the centre of the bad
keypad. Use the ohmmeter to see that the resistance has lowered to less than twenty
(20) ohms. If this does not solve the problem, the trace between the two keypads
may be at fault. This will likely only be the case if you have creased that
section of the membrane. To ensure that both keypads are not at fault, first check
the key adjacent to that which you used to test the connection for your known bad
keypad. Once the second pair of keypads tests good, you can draw a new trace using
conductive paint between the bad keypad and the next closest one. Paint right over
the green insulating layer as necessary and test again to ensure that the
connection is now decent. Let all this paint cure thoroughly before sandwiching
the membrane layers together again. But, as noted above, NO HEAT—okay?
Continue cleaning the other parts and prepare for assembly and test.

Reassembling for Testing Purposes

Taking into consideration the final resting spots of all the components that
make up these keyboards you may soon realize just how far you must reassemble the
parts before a proper and reliable test may be performed. The membranes have to be
firmly sandwiched to the back plate, which means all the key buttons must be
placed back into the mold and that mold must be fastened to the back plate using
all thirty-nine (39) screws to ensure even pressure and good contact reliability.
The grounding wire should also be connected and to obtain a connection to the
computer, the printed circuit board (PCB) must also be mounted to the back plate.
Of course the key caps must be in place and all the minute details of these
wonderful tidbits are presented below.

First consider Tom Fine’s excellent suggestion: If
you are concerned only with knowing whether or not your circuit trace repair
operation worked, you probably can accomplish this without reassembling the
keyboard to the same degree reported below. Reconnect all the electrical
connections that go from keyboard back to the computer, then simply push the
keyboard membrane layers together (where there would normally be a keycap) with
your fingers and you should register a keypress if your repairs were successful.
You may get inconsistent results with this method, but if it works at all (where it
did not before) you can be pretty certain your repair worked.

Tom mentions one other caveat here: If you apply too thick a layer of conductive
paint, you may get false triggering of keys that you repaired (or possibly
surrounding those keys) when you put the screws back into place during reassembly.
Test this first by pressing the membranes together where the screws would normally
hold the layers to the back plate, and if you get erratic behaviour try reducing the
thickness of your conductive paint repair(s) by using a fine and sharp knife, some
400 to 600 grit sandpaper, an abrasive eraser such as those used for pen ink, or a
similar process.

Continuing on, it is often the case that all thirty-nine (39) screws need not
necessarily be put back in place for testing the keyboard. In fact, you may not
want to use more than a few around the outside edges to save wear and tear on the
screws and the key button mold. Just be aware that if you use only a few screws
and you find that one or two keys do not work during testing, it may be due to the
fact that the plates are not being held together well enough. Insert more screws
around that area and try again before assuming the keys do not function. Be aware
also that the screws are made of very soft metal so do not use a lot of force to
tighten them.

As if it wasn’t obvious, the photo at left depicts the method of placing the
key buttons into their mold—all one hundred eight of them! Place the mold on
a flat surface and place all the key buttons in their spots. The photo at right
shows what the small green LEDs look like. There are two such devices: one goes
under the CAPS LOCK key, and the second goes under the NUM LOCK key at the top of
the numeric keypad portion of the keyboard.

At left is a photo showing the LED in its place in the key button mold. The photo
on the right shows the keyboard membrane at a point where one set of LED contacts
can be seen. The two square pads near the centre of the image are what rest
against the leads of the LED when the keyboard is properly assembled. The LEDs fit
one way only into their respective places in the mold, so you need not worry
about polarity issues.

There are two clear jelly-like strips (photo at left) that must be placed in
their proper spots on the mold as well. The photo at right shows one of those
spots. Both are near the top edge of the key button mold. These pressure strips
force the membrane edge contacts to mate with those found on the PCB itself. The
edge connections transfer signals between the keyboard matrix and the computer
via the USB cable.

At left is a look at the printed circuit board side of the edge contact
mechanism. These contacts are regular PCB traces—usually copper, sometimes
gold plated—with a conductive mound of material screened on them, then
cured in an oven. These mounds are not exactly smooth, making the connections more
reliable by virtue of the fact that more points of contact can be realized with an
uneven pad rather than a perfectly smooth one. The photo at right shows the mating
edge connector of the keyboard membrane. This portion of the membrane rests over
the pressure strip and the two holes in the membrane align with two posts in the
key button mold at either end of the pressure strip.

Place the keyboard membrane over the key buttons in the mold after the
pressure strips have been installed, then place the back plate over the whole
assembly and ensure that everything lines up properly. Once you are certain that
everything is perfectly aligned, replace the thirty-nine (39) screws that hold the
mold against the backplate. DO NOT apply any form of mechanic’s
torque to these screws whatsoever! All they need to do is keep the mold
pressed against the back plate enough to ensure the membrane is well sandwiched.
This means no power tools at all, and use a #1 Philips screwdriver with a handle
having a diameter of one (1) centimetre or less. This helps prevent the possible
application of too much torque on the fragile plastic mold when strong folks
attempt the procedure! Also, when putting screws back into plastic pieces it is
better to first rotate the screws counter-clockwise until they click into place.
Slight downward pressure is needed to feel this click, as if you were about to
fasten the pieces back together with the screw, but you turn the screw in the
opposite direction. Once it clicks you know the screw threads have fallen into the
spiral grooves already present in the plastic from the original assembly process.
It is at this point that you turn the screw clockwise to properly fasten things
together, and you know that the screw will be using the pre-cut grooves in the
plastic instead of carving a new path for itself every time you replace the screw.
This little trick will save you from stripping the screw holes inadvertently, so
long as you do not over tighten the screws, of course.

Before the PCB can be attached to the back plate, this thin plastic insulator
must be aligned over the back plate to prevent the possibility of any exposed
traces on the PCB from shorting out on the back plate when the keyboard is
assembled. This film has several holes punched into it which only line up one way
with holes in the mold and backplate, so locating the correct placement should be
relatively easy.

Be sure to use the correct screws when mounting the PCB to the back plate. The
brass-like pan head screws are the only ones of their kind found in the entire
keyboard assembly.

Don’t forget to reattach the grounding screw before bringing the whole mess
over to your Mac for a test.

Testing Your Handywork

Testing is ultra easy. Plug your USB mouse into either port on the keyboard to
see that the port works when you boot the computer. Change the mouse over to the
other port or use a second USB device to ensure that nothing happened to the other
USB port. Should anything have happened to the correct function of the USB ports
at this stage, you will have to troubleshoot. Look for loose or broken wires, and
failing that you may have zapped a component on the PCB with static electricity
while you were working with it. Either scenario is highly unlikely if you treat
everything with care throughout the process of disassembly, cleaning and
reassembly.

Use the “Keycaps” application in Mac OS 9 to
test the function of each and every key on the keyboard. Tom Fine wrote in to
suggest a method for use in OS X 10.4 (Tiger,) which includes following this chain
of command: System Preferences -> International -> Input Menu and then turning on
the Keyboard Viewer option you will find there.

Once you have a method of seeing a result, try each key several times and
always try keys on an individual basis only. If more than one key icon in the
application is shaded for a single key pressed, you’ve got a short
somewhere. The exceptions here are those keys which are duplicated, like the
OPTION, SHIFT, CONTROL or APPLE keys.

If you have a short or if a key still does not function correctly, you have
more work to do. Take the more than 160 pieces apart once again and revisit the
membrane for another look. Once testing proves successful, a full reassembly is
in order.

Full Reassembly

It’s pretty straightforward to continue assembling the rest of the bits
and make it look like a real store-bought Apple Pro Keyboard again. To begin,
remove the PCB from the back plate once again. This is necessary to enable easy
application of the decorative back plate cover, which is just a silvered piece of
card stock with a sticky outer edge. Align the card cover over the back plate and
apply medium pressure to the edges all the way around and also apply pressure at
the hole in the centre. Once the card is in its place, reattach the PCB to the
back plate and continue the reassembly process.

In the photo at left, the USB port is almost seated correctly in the bottom outside
mold for the keyboard. This is a reference photo only since the PCB cover must be
installed before the keyboard assembly is mounted into the bottom shell anyway. The
photo at right shows how the PCB cover also holds the USB ports in place.

This is one of two identical retainer clips which hold the keyboard’s
height adjustment bar to the bottom shell. If you have taken these out in your
cleaning process, put them back in now and check their function by moving the
adjustment bar to both positions. The top portion of this clip (as
shown in the photo at right) faces toward the inside of the keyboard. The pin in
the middle engages the height adjustment bar. Thanks go to Greg for the photo
and explanation.

Place the PCB cover in the bottom shell as illustrated and prepare to set the
keyboard in place. Before replacing the keyboard be sure to remove the three keys
that cover the small Philips holding screws. These keys are the CAPS LOCK,
semicolon (;) and numeric keypad number six (6) keys.

The photo on the right shows the cable strain relief clip that fits over the
strain relief mold around the keyboard cable. Before the keyboard is perfectly
aligned in the bottom shell this strain relief will have to be assembled as its
screws will not be accessible once the keyboard is in place. Ensure that the flat
part of the strain relief molding on the cable itself is seated in the bottom
shell. This leaves the rounded part which goes into the strain relief mounting
clip shown in the photo. The strain relief clip also fits snugly into its own
spot in the bottom shell, so be certain to align it correctly in the shell also.

This is what the finished strain relief assembly looks like before the keyboard is
placed correctly into the bottom shell. Note the plastic cover at the top of the
keyboard that will interfere with the strain relief clip screws. This cover would
prevent the use of a screwdriver to remove the strain relief clip before the
keyboard is free of the bottom shell.

This is the type of screw that goes into the strain relief clip. This same type of
screw is used to hold the PCB cover and keyboard back plate to the bottom
shell—the screw that hides under the Pro Keyboard label.

Align the keyboard assembly in the bottom shell so that all screw holes line up and
also ensure that the PCB cover and USB ports are seated correctly in the shell and
against the keyboard back plate. There are a couple more small plastic covers to
add before the top shell can be placed over the keyboard, one of which is
illustrated in this photo. The slightly coloured area represents the plastic
cover that rests between the numeric keypad and the main alphabetic portions of
the keyboard. This cover has the shape outlined in colour, and at the upper tips
is formed so that a small bit of each tip—about six millimetres or
so—is angled about forty-five (45) degrees from flat inline with the rest of
the cover. These angled tips should face downward, toward the back plate of the
keyboard assembly.

The other two plastic decorative covers consist of one white and one
transparent cover, both of which have exactly the same shape. These
covers—white under clear—align at the top of the keyboard between the
upper row of keys and the top edge where the USB ports protrude from. There is a
hole at each end of these covers that align with two pins in the top shell.

Place the top shell over the whole mess starting at the top edge where the USB
ports sit and be careful aligning everything as you go. Work the top shell into
its place and be careful when snapping it together with the bottom shell at the
edge where the SPACE BAR resides. The snaps will break easily, so engage them one
at a time and try to push the top shell a bit toward the USB ports while seating
each snap over its nib on the bottom shell. You’re almost there!

Don’t forget to replace those three screws which hide under the keys of the
keyboard. After they are in place, push the key caps back in their spots and
continue replacing the rest of the screws from the underside of the keyboard.
These include the one that normally hides beneath the Pro Keyboard label, and the
four hex screws that go into the holes near the left and right top edges. Take a
look at the next three images to see where each key cap fits on the keyboard.

This image shows the left-hand side of the keyboard which will be useful in
finding the appropriate spots for each of the key caps currently strewn about your
work area.

Here is what the centre portion of the keyboard should look like once all the
key caps have been installed in the proper places.

And finally, the right-hand side of the keyboard including the numeric keypad.
The keys on the numeric keypad have only one symbol on each of them versus the ones
on the numeric row of the main keyboard area which have two symbols per key. Each
key cap belonging in the extended keyboard area (numeric keypad included) is
unique. The cursor keys can be tricky. The one that points up is the only one with
a concave key cap. The rest have a convex shape to their tops. Note also that the
arrow markings of the cursor keys are positioned in the lower left portion of each
key cap. One more note about unique keys: Tim Tisdall emailed to point out that
the control keys are slightly different. The one belonging on the left
side of the keyboard has a more rounded bottom-left corner, while the one
belonging on the right side sports a bottom-right corner that is more rounded
than the others.

For the UK version of this keyboard, the key caps often show symbols in place
of English text, and a couple of keys are in different positions, or are of a
different shape. My thanks to Peter Neill for the heads-up on this, and the
diagram. Here is the left side portion of the UK layout.

The centre portion of the UK layout.

The right-hand side of the UK keyboard layout completes the job.

Now that all the key caps are in their proper spots, that is it! Your keyboard
should look and function like new. Give yourself a well deserved pat on the back
and go get some grub; this has been an arduous task!

Conclusion

This process is an involved and delicate one. Time consuming is not the phrase
to describe this effort from a first-try perspective. About ten (10) hours were
spent on it figuring out the safest way to disassemble everything and documenting
the process with digital photographs. Now that this web page exists, the estimated
full disassembly, cleaning and reassembly process should take no more than a
couple hours on a first-time try, and even less time, should you ever have to do
this more than once.

It is important to note that none of this is necessary when users take care to
keep their food and drink away from the computer. Most people have swivel chairs
in front of their machines making it very easy to set the foods in a completely
separate area and swing around for a bite or a swig as necessary.

The case for this keyboard is that it is attached to a G4 powerhouse which
runs the Final Cut Pro 2 non-linear editing software used for college film and
television project editing. Students need not be reminded about the end of term
and the flurry of activity everywhere as each scrambles to complete his or her
project(s) before critical submission deadlines. When a keyboard is taken out
of commission and has to be cleaned of spilled soda or other foods it could mean
that a project goes unfinished and the final marks will reflect that. Accidents
like this are completely avoidable and in light of the fact sometimes keyboards
cannot be repaired at all, it should be obvious to all users that there is no
benefit to force feeding a keyboard human foods. It can take days or weeks to
replace a keyboard that cannot be repaired. The cost here is just under $100 to
replace one of these keyboards, so spares are not kept on hand. Food for thought.

Other Potential First Aid Measures

You, as the repair technician or as the owner of the hungry keyboard might
have thought of these ideas already, but in case you have not, other first aid
options exist:

Immediately after a soda spill, unplug the keyboard and immerse in a bath of
distilled water,

Immerse the keyboard in a bath of alcohol (for a period of a few minutes, no
more, or

Attempt to force the remaining liquid out using compressed air

Some measures are inherently risky, especially the alcohol bath, because the
grease can be dispersed by the alcohol and it may gum up the works elsewhere in
the keyboard. Also, if the grease is cleaned away from the wire supports under the
larger key caps those caps may be damaged by the lack of lubrication. Alcohol
baths can damage or at least discolour parts of the keyboard assembly, so use
good judgement here.

If alcohol or distilled water is used to clean away liquid spills immediately,
there is little chance of any chemical reactions that can cause keys to
malfunction, but with the alcohol bath—though it will dry out much more
quickly—the grease under the keycaps must still be replaced. With distilled
water the drying time can be days, but the grease will likely
not disappear. Either way the keyboard is out of commission for a while since both
liquids should be dried completely before you can test it again.

It is advisable in both instances to disassemble the keyboard in its entirety
afterward anyway because there is a good chance that not all the foreign liquid(s)
will be washed away by the bathing process. Damage can still occur unless
everything is thoroughly clean like it was when assembled at the factory the
first time. The baths may be used as a first aid measure simply to lessen the
chances of massive damage—but nothing is guaranteed, and the baths
themselves might cause damage also—especially if the keyboard is still
plugged into the computer.

As for the compressed air option, take a look at this photograph. The hole just
above and to the right of the big cola bubble is how the soda got to the inner
layers of the keyboard. Cola was found everywhere from under some of the key caps
all the way to the bottom shell, and at every layer in between. It is doubtful
that any dose of compressed air will clean liquid away well enough, but if
it’s all you’ve got, it’s better than letting soda pop sit idle
to eat away at the innards of your keyboard.

Links to other Helpful Web Places

Assistiveware.com
sells—among other titles—KeyStrokes , which is a utility
allowing a user to enter textual information using a device other than the
keyboard. This could be good if you and your keyboard enjoy a drink together!

The homepage of the Niagara College
Technology web space. This
keyboard repair web page is a direct result of a mishap with one of the
college’s keyboards and as such it is hosted there. There are many other
interesting topics covered in the pages under this link in the Faculty and
Staff section, so enjoy your time here.

This page is now five years old! My thanks to all who continue to write in
with their experiences and suggestions, as there have been many improvements to
the original article resulting from your suggestions.

2 July 2008 — Tom Fine wrote in to suggest a
replacement for the
Keycaps application (from Mac OS 9) in Tiger, and possibly others. He also
suggested that it is not necessary to reassemble the keyboard to do
preliminary tests
on key functionality. He also suggested that you might find a conductive pen
made by MG Chemicals for about $20 in many North American electronics component
retail outlets.

13 February 2008 — David Wolinetz had tried using a 4B pencil to redraw
broken traces with graphite, and reported it does not work well enough to solve
the issue. I have removed suggestions of using a pencil to redraw traces from
this document as a result.

2 November 2007 — Peter Neill indicated that the UK version of this
keyboard has a
different layout
than the US version with different symbols on the key caps. He also did some
painstaking work on the bitmap image to illustrate those finer points.

19 February 2007 — Joe Wheeler suggested that a Torx 5 (T-5) driver
will work in place of a proper sized hex driver for the screws on the underside
of the keyboard. He also suggested Vaseline as a substitute for the grease on the
larger key supports (such as the spacebar) should you need to replace that
lubricant.

4 January 2007 — David Roth made the excellent suggestion of placing a
list of required tools at the top of the document in case anyone needs to go
shopping.

2 October 2006 — Gregor Komauer has found a set of tools that may
be available throughout Europe. The brand is Lux Tools from Germany, product code
585 395 (EAN code 4007875853959). Gregor claims the set has everything you need
for working on these keyboards. Take a look at a product photo at the top of
the
disassembly section of this web page.

29 August 2006 — Ian Lanham wrote in to say—much to his
chagrin—that leaving the key button mold soaking in isopropyl alcohol
is a bad idea as it will discolour the mold or possibly damage it.

18 July 2006 — Greg from Redondo Beach, California sent a picture of a
retaining clip which holds the keyboard height adjustment bar. Look into the
description of it and how to put it back in place in the
reassembly
section of this document.

19 June 2006 — Payne Freret suggested that you could peel away the sticker
that hides a screw on the back side of the keyboard. If carefully done, you can
reapply the sticker during reassembly and it will look as new and not have a hole
in it as I originally suggested. You can read about the details of this
careful procedure
here.

3 August 2005 — Bob Palmer had more luck separating the top and bottom
keyboard shells using a nail file and prying at the back edge as opposed to the
front edge as originally proposed in this article. Take a look at the
top shell
and corresponding instructions.

4 Mar 2005 — Rick Mullaney suggested that the model number of the
Pro Keyboard should be visible in the article. At that, I have posted the model
number of the keyboard used for this article in the title bar and at the
beginning of the text also.

23 Aug 2004 — Tim Tisdall pointed out that the control keys
are slightly different from one another. You will find the details in the
reassembly section of this document.

Stephan Kurz—who emailed me several months ago—has completed
repairs on his Apple USB Keyboard. Stephan used some unorthodox methods to get
his functioning again and he has documented it all on his website. Look in the
links section to visit his web page on the matter.

18 Jun 2004 — Mike Skaggs suggested using a metal or stiff plastic
bookmark to remove the silver-coloured card stock from the keyboard backing plate
as a way to preserve the integrity of the card stock while easily removing it to
get at the screws beneath. You will find all the gory details in the
Disassembly section of this page.

26 Nov 2003 — I learned how to spell the word theory :-)
Also, the PDF version has been dispensed with in favour of Cascading Style Sheets
which change the web page based on your viewing medium. This means black print on
a white page, like a traditional printout, simply by hitting your browser’s
print button. If you are having difficulties with printing from this
new version the
PDF is still online, but it no longer will be updated with changes. It seems
IE6 on a Windows box chops images because it does not know enough to go to the
next page if an image is too near the bottom margin. I am working on a solution,
though nothing is perfect. Some other browsers automatically move images to the
next page so they remain intact. Perhaps a browser upgrade is in order if you are
experiencing this problem.

19 Nov 2003 — Philip Bell suggested a method of ensuring that screws
being replaced into plastic parts of the keyboard do not strip out the grooves
in the plastic. Under the
Reassembling for Testing section is where you will
find this technique described.

21 Oct 2003 — I’ve added a note about using rear window defogger
repair paint to the section on
repairing a digested keypad, as suggested by a reader who
sent me an email saying how well it worked for him. Unfortunately, I have
misplaced his email to give proper credit, but I will find it and post it when
I do.

4 Sep 2003 — Stella Wu suggested that a keyboard map would be helpful
for placing the keycaps back in the proper order during reassembly. Also new
is the emphasis made regarding the necessity to puncture the plastic-like sticker
near the serial number to access the hidden screw underneath. These new items are
found in the
reassembly and
disassembly sections, respectively.